Thermochronological, Petrographic and Geochemical Characteristics of the Combia Formation, Amagá Basin, Colombia

Thermochronological, petrographic and geochemical characteristics of the Combia Formation, Amagá basin, Colombia Matthias Bernet, Juliana Mesa Garcia, Catherine Chauvel, Maria Ramírez Londoño, Maria Marín-Cerón To cite this version: Matthias Bernet, Juliana Mesa Garcia, Catherine Chauvel, Maria Ramírez Londoño, Maria Marín- Cerón. Thermochronological, petrographic and geochemical characteristics of the Combia Forma- tion, Amagá basin, Colombia. Journal of South American Earth Sciences, Elsevier, 2020, 104, 10.1016/j.jsames.2020.102897. hal-02990433 HAL Id: hal-02990433 https://hal.archives-ouvertes.fr/hal-02990433 Submitted on 17 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 Thermochronological, petrographic and geochemical 2 characteristics of the Combia Formation, Amagá basin, Colombia 3 4 Matthias Bernet1*, Juliana Mesa Garcia2,3, Catherine Chauvel1,4 5 and Maria Isabel Marín-Cerón2, 6 1Institut des Sciences de la Terre, CNRS, Université Grenoble Alpes, Grenoble, 7 France 8 2Departemento de Geociencias, Universidad EAFIT, Medellín, Colombia 9 10 3present address: Geology Department, University of Michigan, Ann Arbor, MI, USA 11 12 4Université de Paris, Institut de Physique du Globe de Paris, CNRS,F-75005 Paris, 13 France 14 15 *corresponding author, email: [email protected], 16 ORCID: 0000-0001-5046-7520 17 18 19 Abstract 20 The Amagá basin between the Western and Central Cordilleras of the 21 Northern Andes of Colombia host the Neogene volcanic and volcaniclastic Combia 22 Formation. At this stage it is not clear how the formation of this unit is related to arc 23 volcanism and which role the Nazca plate subduction beneath the western margin of 24 South America plays. The timing, petrography and geochemical characteristics of 25 Combia Formation rocks were studied in the western and eastern parts of the 26 Amagá basin, in order to gain more information on the type of magma generation 27 and volcanic activity that led to the deposition of the Combia Formation. 28 Apatite and zircon fission-track dating largely confirm a 12-6 Ma age for the 29 deposition of the Combia Formation. Petrographic and major element analyses show 30 that mainly trachy-andesite ignimbrites with a calc-alkaline composition were 31 deposited in the western Amagá basin, whereas the volcanic rocks of the eastern 1 32 Amagá basin are lava flow and fall-out deposits of basaltic andesites or of tholeiitic 33 composition. Trace element and isotopic analyses show that slab dehydration and 34 sediment melting were important in primary magma generation in the mantle wedge, 35 but the primary magma was mixed with lower continental crustal melts, resulting in 36 characteristic isotope signatures in the western and eastern Amagá basin. All this 37 points to subduction driven arc volcanism with slab dehydration, sediment melting 38 magma mixing. 39 40 41 Introduction 42 The late Paleogene to present-day magmatism of northwestern South 43 America can be divided into four major phases of activity at about 24-20 Ma, 12-6 44 Ma, 6-3 Ma, and 3 Ma to the Present (e.g. Sierra, 1994; Toro et al., 1999; Gonzalez, 45 2001; Ramírez et al., 2006; Cediel et al., 2011; Pérez et al., 2013; Lesage et al., 46 2013). These different magmatic phases are related to the complex tectonic setting 47 in which the Caribbean, Nazca and South American plates interact with each other 48 (Fig. 1). The break-up of the Farallón plate into the Nazca and Cocos plates between 49 26 and 24 Ma (Marriner and Millward, 1984), the reorientation of subduction 50 direction (Pardo-Casas and Molnar, 1987), and collision of the Panamá-Choco block 51 with northwestern South America at about 25 Ma drove the first magmatic pulse (e.g. 52 McCourt et al., 1984; Aspden et al., 1987; Kellogg and Vega, 1995; Trenkamp et al., 53 2002; Cediel et al., 2003; Lonsdale, 2005; Restrepo-Moreno et al., 2010; Farris et 54 al., 2011). Second, since the late Paleogene the Nazca plate subduction zone was 55 subjected to changes in subduction angle and direction over time, resulting in 56 Miocene-Pliocene magmatic intrusions in the Western and Central Cordillera and 2 57 deposition of the Combia Formation in the Amagá basin (e.g. Pardo-Casas and 58 Molnar, 1987; Taboada et al., 2000; Cediel et al., 2003; Vargas and Mann, 2013). At 59 the same time, subduction of the Caribbean plate beneath the northern (Caribbean) 60 margin of South America caused isolated late Miocene-Pliocene volcanic activity in 61 the Eastern Cordillera (e.g. Vargas and Mann, 2013), such as in the Vetas-California 62 gold-mining district of the Santander Massif (Mantilla et al., 2013), or the Paipa-Iza 63 complex 150 km to the north-east of Bogotá (Fig. 1; Padro et al., 2005; Bernet et al., 64 2016). Today the main volcanic activity in Colombia is focused on the Central 65 Cordillera with for example the Nevado del Ruiz, Nevado del Tolima, Cerro Machín, 66 Nevado del Huila, Azufral, Cumbal, etc. well to the south of the study area (Fig. 1; 67 e.g. Marín-Cerón et al., 2010, 2019; Leal-Mejía, 2011). 68 Different techniques have been used for more than a century to understand 69 the genesis, age and evolution of the Combia Formation, including petrography, 70 heavy mineral analysis, X-ray diffraction, geochemistry, geochronology, 71 thermochronology and stratigraphic analyses (e.g. Grosse, 1926; Jaramillo, 1976; 72 Calle and González, 1980; Álvarez, 1983; Marriner and Millward, 1984; Rios and 73 Sierra, 2004; Pérez, 2005; López et al., 2006; Ramírez et al., 2006), but the 74 evolution of the Nazca plate subduction zone magmatism still remains poorly 75 constrained. Here we present a study of a suite of samples collected from three 76 sections, the Cerro Amarillo section in the eastern Amagá basin, and the Anzá- 77 Bolombolo and La Metida Creek sections in the western Amagá basin (Fig. 2), in 78 order to improve the knowledge gained so far about the Combia Formation. The 79 volcaniclastic, tuff/lapilli and flow deposits of the Combia Formation were examined 80 with a) apatite fission-track (AFT) and zircon fission-track (ZFT) thermochronology, 81 b) petrographic analyses, and c) major and trace element analysis, as well as Sr, Nd 3 82 and Pb isotope analyses. All this was done with the objective of a) characterizing 83 and comparing the eastern and western volcanic deposits, and b) to better 84 understand the mid-late Miocene evolution of the Nazca subduction zone 85 magmatism manifested between the Western and Central Cordilleras. 86 87 Geological setting 88 The Northern Andes of northwestern South America consist in Colombia of 89 the Western, Central and Eastern Cordilleras (Fig. 1). Each of these mountain belts 90 reflects a particular part of the long-term evolution of the Northern Andes, which is 91 characterized by magmatic episodes since the Precambrian, during the Triassic, 92 Jurassic, Late Cretaceous, and since the late Paleogene/Neogene until today 93 (Aspden et al., 1987). In general, these magmatic phases have been related to 94 Farallón/Nazca plate subduction beneath the western margin of the South American 95 plate (e.g. Marriner and Millward, 1984; McCourt et al., 1984; Cediel et al., 2003; 96 Saenz, 2003; Restrepo-Moreno et al., 2009; Rodríguez et al., 2012). Accretion of 97 tectonic blocks or terranes of oceanic affinity to the continental margin during the late 98 Mesozoic and early Cenozoic did not cause Andean-type subduction volcanism, 99 because of their relatively young age and high buoyancy preventing subduction 100 (Cediel et al., 2003), and forcing surface uplift and the formation of the Western and 101 Central Cordilleras during the Pre-Andean and Andean orogenies (e.g. Van der 102 Hammen, 1960; Taboada et al., 2000; Cediel et al., 2003). 103 The present-day Andean volcanism is commonly divided into four volcanic 104 zones, the Northern Volcanic Zone (NVZ), Central Volcanic Zone (CVZ), Southern 105 Volcanic Zone (SVZ), and Austral Volcanic Zone (AVZ) (e.g. Thorpe and Francis, 106 1979; Thorpe et al., 1982; Stern, 2004; Marín-Cerón et al., 2019). These segments 4 107 have been distinguished based on differences in petrographic features and 108 geochemical signatures, and they are separated from each other by volcanic gaps 109 (e.g. Thorpe and Francis, 1979; Stern, 2004). The NVZ is located in north-western 110 South America and encompasses the region of present-day volcanism in the 111 Northern Andes of Ecuador and Colombia. 112 113 Geology of the Amagá basin 114 The Amagá basin forms the northern part of the much larger Amagá-Cauca- 115 Patía basin located between the Western and Central Cordilleras of the Northern 116 Andes in western Colombia (Fig. 1; Sierra and Marín-Cerón, 2011). Dextral strike– 117 slip faulting along the Cauca and Romeral fault systems to the west and east 118 respectively is responsible for development of the Amagá basin, which is tectonically 119 a pull – apart basin (e.g. Cediel et al., 2003). Basin evolution started possibly during 120 the Eocene (?) – Oligocene, with surface uplift and erosion of the Central Cordillera 121 from the Late Cretaceous to Eocene and deposition of clastic sediments of the 122 Lower Amagá Formation in the basin (e.g.

Load more